Inductive coupling of toroidal coils



Sept. 20, 1960 R. E. LAFFERTY 2,953,756

- INDUCTIVE COUPLING OF TOROIDAL cons Filed Jan. 6, 1959 n ma MAX- INDUCTANCE M N INDUC ANCE V Fl G. 5

I3 I l l6 g HH JEH'JHE RAYMOND ELAFFERTY n 3% I FIG. 4

United States Patent INDUCTIVE COUPLING F TOROIDAL COILS Raymond E. Lalferty, Fair Lawn, N.J., assignor to The Daven Company, Livingston, N.J., a corporation of New Jersey Filed Jan. 6, 1959, Ser. No. 785,261

3 Claims. (Cl. '33377) This invention relates to an improved means for coupling toroidal inductor elements used in multi-stage filter networks and the like type of apparatus for adjusting band-pass characteristics.

Where there are two or more toroidal type elements a mutually inductive factor can exist and can be adjusted by regulating the coefficient of magnetic coupling, the coeflicient of magnetic coupling between any two inductors being a measure of the completeness with which the magnetic flux of one inductor embraces that of the other.

Various methods have been proposed for accomplishing this interrelation between toroidal coils: for example, toroidal coils have been top-coupled, that is, mounted one above the other with the respective coils constructed with suitable open sections adapted to be adjusted relative to each other; toroidal coils have been loop-coupled by a continuous ring of current-conducting material extending through the respective openings on a pair of adjacent toroidal coils, the inductive effect being adjusted as a function of (a), the conductor; (b), the spatial relation of the coil elements, and (c), a reactive element placed in the conductive loop; and toroidal inductors have also been top-coupled by means of capacitive elements.

However, these methods have many disadvantages. For example, where capacitors are used as in top-coupling, owing to the hiatus in the values of commercially available capacitors it is diificult to set the desired degree of coupling. Similar and other disadvantages are known in the other suggested methods of inductive coupling.

The present invention overcomes many of these problems by providing an improved inductive coupling arrangement for a plurality of toroidal coils consisting of mounting means for the respective toroidal coils where'- in each mounting means has a predetermined length and serves as a fractional turn of the coupling loop and the mounting means are interconnected by an adjustable control inductor so that at each stage when the electrical effect of the common chassis support the mounting means, and the control induction are taken into account, the toroidal coils will be coupled by a loop of current-conducting material adjustable for any desired degree of coupling.

Accordingly, it is an object of the present invention to provide an improved loop-type coupling means which is relatively inexpensive to manufacture and provides simple means for adjusting the inductive coupling between toroidal coils.

Further objects and advantages of the invention will become evident from the following description with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic illustration of the prior art loop-type arrangement.

Figure 2 is a diagrammatic illustration of a plurality of toroidal coils mounted on a fragment of a chassis showing the invention.

Figure 3 is a view taken on lines 33 of Figure 2.

Figure 4 is another form of mounting post.

Figure 5 is one form of control inductor shown in maximum and minimum inductive coupling position.

Figure 6 is another form of control inductor.

Figure 7 shows the electrical configuration for a plurality of toroidal coils using the same type loop arrangement.

Referring to the drawings, Figure 1 shows diagrammatically a loop-type coupling of two toroidal coils used or shown in the prior art wherein A and B represent the toroidal coil elements which are joined by a continuous current-conducting line C having an inductive element D mounted therein. This mechanism presents many difficulties particularly that of holding the toroidal type coils in the desired spatial relation which effects the inductive coupling obtained by this arrangement.

Figure 2 shows a preferred form of the present invention wherein the chassis provides the common for the circuit.

The improved loop arrangement includes a plurality of mounting means 2a, 2b and 20, etc. connected at spaced intervals along the chassis.

The mounting means comprise solid elements which are good conductors of electricity, such as metal or the like. These elements are threaded as at 3 so that each of the toroidal elements 4a, 4b, 4c, etc. may be mounted thereon as by an upper and a lower nut 5 and 6, and washer means 7 and 8, respectively, as shown in Figure 3 of the drawings. While this type of connection for the coils to the mounting means is suggested, it is believed that any other suitable means could be utilized. For example, the coil itself could have an inner section that is self-threading or which has sufficient frictional engagement to hold the coil in position on the mounting means. The relative position of the coil on the mounting means is not significant. However, the length of the effective conducting portion of the mounting means is significant because it forms a fractional turn of the current-conducting loop which joins each pair of coils. Thus, the length of the effective conducting portion of the mounting means 2a, 2b and 2c will be a predetermined fixed value as a function of the coupling desired. If more coupling is desired the effective length of the mounting means will be less. If less coupling is desired then the effective length of the mounting means will be greater.

Figure 4 shows that the elfective conducting length of the mounting means can be made adjustable as by the spaced nuts 20 and 21 with the connecting element 22 held therebetween. This mechanism can be threaded up or down relative its respective toroid and accordingly provides another means for accurately adjusting the inductive coupling between the coils as hereinafter described.

Connected to the respective ends of the mounting means 2a, 2b and 2c, etc. as by soldering or any other suitable means, are the current-conducting lines 9a, 9b and shown in Figures 2 and 3 of the drawings. In each of these respective lines 9a, 9b and 90, a control inductor as at 10a and 10b is provided. These control inductors are of the same or substantially the same construction and one form of control inductor is illustrated at Figure 5 of the drawings as having a non-conductive body portion 11 on which is loosely or slidably mounted a coil of wire 12.

Figure 5 shows that these control inductors provide a means for adjusting inductive coupling between the respective coils to which the loop is connected by the simple process of manually spacing the respective turns of the coil relative to each other until the desired amount of coupling is obtained.

Another form of control inductor is shown in Figure 6 as comprising a cylindrical element 13 of non-conductive material having a coil of wire 14 disposed on the outer surface and a core 15 adjustably connected relative to element 13 as by the threaded support 16 and threaded rod 17. Means 18 at the outer or remote end of the threaded rod 17 provides means for moving the core 15 inwardly and outwardly of the cylindrical element 13 to provide the desired amount of inductive coupling.

The type of material of which the core is made will determine inductive coupling to a degree. For example, if copper or brass or the like alloys are used maximum inductance occurs when the core is out of the coil, as shown in Figure 6, and minimum inductance when the core is disposed centrally of the coil. If the core of material is powdered iron or a ferrite material then the reverse is true.

Figure 7 is a diagrammatic illustration using electrical symbols which shows the circuit for the preferred form of the invention shown in Figure 2 of the drawings. The character numerals m m and m represent the mutual inductance between the loop formed by the respective posts and the adjustable control inductor connecting the respective toroidal coils.

For each pair of coils we find that a loop of currentconducting line includes the grounded mounting means 2a, 2b and 2c, the lines 9a, 9b and 9c, and the respective control inductors a and 10b, applicable to the particular circuit. If the mounting means 2a, 2b and 20 have a fixed length then the desired degree of inductive coupling between the respective toroidal coils is adjusted by the control inductor alone. In the case of the type control inductor shown in Figure 5, the turns of the coil are moved relative to each other manually till the exact degree of inductive coupling desired is obtained.

If the mounting means is adjustable as shown in Figure 4 then the length of the mounting means is first adjusted to the desired predetermined length and inductive coupling is then effected by adjusting the control inductor as above described.

Where the control inductor is of the type shown in Figure 6, a suitable tool is applied to the means 18 and the core adjusted till the desired amount of inductive coupling is obtained.

It will be understood that the invention is. not to be limited to the specific construction or arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. A loop-type inductive coupling means for a plurality of toroidal type coils comprising, a support providing a common ground for the coupling means, a plurality of mounting means formed of current conducting material connected to said support, each of said mounting means adjusted to a predetermined length, a toroidal coil mounted on each of said mounting means, an electrical current conducting line connecting said mounting means, and an adjustable control inductor disposed in said currentconducting line to coact with said mounting means for regulating the desired inductive coupling between said toroidal coils.

2. A loop-type inductive coupling means for a plurality of toroidal type coils comprising, a support providing a common ground for the coupling means, a plurality of mounting means formed of current conducting material connected to said support, a toroidal coil mounted on each of said mounting means, an electrical current conducting line connecting said mounting means to each other, inductor means of predetermined inductance disposed in said current conducting line between each pair of toroidal coils, and means on said mounting means for adjusting the effective length thereof to obtain the desired degree of inductive coupling between adjacent toroidal coils.

3. A loop-type inductive coupling means for a plurality of toroidal type coils comprising, a support providing a common ground for the coupling means, a plurality of mounting means formed of current conducting material connected to said support, means on said mounting means for adjusting the effective length thereof, a toroidal coil mounted on each of said mounting means, an electrical current-conducting line connecting said mounting means, control inductor means disposed in said current conducting line, and adjustable means for said control inductor means to coact with said means for adjusting the length of said mounting means to obtain the desired degree of inductive coupling between at least a pair of toroidal coils.

References Cited in the file of this patent UNITED STATES PATENTS 2,145,561 Toth et a1. Jan. 31, 1939 2,452,560 Gainer Nov. 2, 1948 2,503,923 Silvey Apr. 11, 1950 2,817,719 Decker Dec. 24, 1957 FOREIGN PATENTS 201,104 Switzerland Nov. 15, 1938 

